The event starts at 6am with a 2.4 mile swim in Pennington Flash, followed by a a 112 mile cycle through Lancashire, and finishing with a 26.2 mile marathon course where 30,000 supporters are expected to cheer athletes all the way to the finish line in Bolton town centre.

The professional male athletes will complete the race in 8.5 hours and female pro athletes in 9.5 hours. First timers, from the age of 18 to 70, will be looking to cross the finish line in the 17 hour time limit to gain the Ironman badge of glory.

Eimear Mullan, from Ireland, and Fraser Cartmell, from Great Britain, are among the pre-race favourites.

Olympic medallist Rebecca Romero is turning her hand to triathlons for the first time having represented Great Britain in rowing and cycling. She said: “This time it’s not about winning gold or silver. If I get across the finishing line, it’ll be an amazing achievement.”

Double amputees Simon Harmer and Joe Townsend will be part of the 40-strong Team True Spirit, a charity set up to support injured servicemen.

For Simon, who lost both his legs after stepping on a makeshift bomb while on patrol in Afganistan, this is his first Ironman and his first triathlon since losing his legs in 2009.

Simon said: “This will certainly be a challenge and I’m looking forward to it. I just really hope that I will be able to finish it. I’m doing this to make my family proud and to help the charity - without them life would be an awful lot harder.”

Francie Clarkson will also be part of Team True Spirit. She turned 50 this year and has had to learn to swim. She said: “However amazing it is for an able bodied athlete to complete an Ironman, for the wounded serviceman it is truly remarkable.”

Managing Director Ironman Britain and Ireland, Kevin Stewart, said: “The facilities of Bolton and the surrounding countryside offer a superb platform for staging such an iconic event and we very much hope spectators will come and support the athletes throughout their race.”

Leader of Bolton Council, Councillor Cliff Morris, added: “Ironman brings thousands of people into Bolton and vast economic benefit to the town. It is a real test of endurance and we hope the people of Bolton will come out once again, and get behind the athletes.”

Spectators can view the event from Pennington Flash, where the swim starts at 6am, and Victoria Square in Bolton town centre, where the first athlete is expected to finish around 2.30pm.

For further information on the event please visit the Ironman website.